Punching tool having interchangeable punches

Abstract

A punching tool for use in a tablet making machine includes a body portion having at least one bore extending from an end of the holder a preselected distance into the holder. The bore is internally threaded a preselected depth. An interchangeable punch is threaded into the punch holder bore and extends a selected length from the holder. The end of the punch has an externally threaded portion and a cylindrical portion. The cylindrical portion is positioned between the threaded portion and the portion of the punch that extends outwardly from the holder. The cylindrical portion has a diameter that permits it to move freely without interference into and out of the internally threaded bore. The bore has an enlarged thread configuration provided with cylindrical bearing surfaces between threads. The punch threaded portion has a thread configuration corresponding to the configuration of the threaded bore to permit rapid engagement and disengagement of the punch in the bore. The bearing surfaces of the bore stabilize the punch in the bore to maintain the required length of the punch extending from the holder.

I claim: 
     
       1. A punching tool adapted to receive a replaceable punch comprising, a punch holder having a body portion with one end portion and a second end portion,   a bore having an internally threaded portion of a preselected length and diameter extending from said one end portion into said punch holder to a closed end,   a punch having an elongated body of a preselected length including a shank portion positioned in said bore internally threaded portion and an end portion extending outwardly from said holder one end portion,   said punch shank portion having an externally threaded portion and a cylindrical portion,   said cylindrical portion being positioned between said shank portion threaded portion and said punch end portion,   said cylindrical portion being freely movable in said bore internally threaded portion,   said punch end portion including a torque receiving portion adjacent said cylindrical portion for rotatably advancing said punch shank portion into said bore internally threaded portion,   said bore internally threaded portion including internal threads having a preselected configuration formed by a plurality of thread roots being separated by crests, said crests having a cylindrical shape to form cylindrical bearing surfaces between said thread roots,   said punch portion shank externally threaded portion including threads having an enlarged thread configuration corresponding to the configuration of said bore internal threads to permit rapid engagement and disengagement of said punch shank portion externally threaded portion with said bore internal threads upon rotation of said punch end portion, and   said threads of said punch portion shank externally threaded portion being engageable with said bore internal threads such that said cylindrical bearing surfaces of said bore internally threaded portion receive said punch shank portion to stabilize said punch shank portion in said bore to assure positive engagement of said punch shank portion in said internally threaded bore and prevent damage to the meshing threads upon insertion and removal of said punch in said bore.   
     
     
       2. A punching tool as set forth in claim 1 which includes, stop means positioned in said bore adjacent said bore closed end portion for forming a seat for receiving said punch shank portion,   said punch shank portion including an end portion positioned in said bore, and   said punch shank portion being threadedly advanced into said bore until said punch end portion abuts said stop means to limit further movement of said punch into said bore.   
     
     
       3. A punching tool as set forth in claim 2 in which, said stop means includes a plug located in a preselected position in said bore such that abutment of said punch with said plug in said bore positions said punch for a preselected length of said punch end portion to extend from said holder.   
     
     
       4. A punching tool as set forth in claim 1 in which, said punch shank portion cylindrical portion includes a reduced diameter portion, and   said punch shank portion externally threaded portion extending from said reduced diameter portion to the end of said shank portion in said holder bore so that said punch shank portion cylindrical portion is separated from said externally threaded portion by said reduced diameter portion.   
     
     
       5. A punching tool as set forth in claim 1 in which, said torque receiving portion is positioned between said punch shank portion and said punch end portion extending from said punch holder, and   said torque receiving portion being formed by a plurality of planar surfaces for receiving a rotational force for advancing and retracting said punch into and out of said bore in said punch holder.   
     
     
       6. A punching tool as set forth in claim 1 in which, said punch holder includes a plurality of said bores spaced from one another in spaced parallel relation and extending a preselected depth into said punch holder body portion, and   a plurality of said punches being releasably engageable in said bores respectively to provide said punch holder with a plurality of said punches each extending a preselected distance from said punch holder.   
     
     
       7. A punching tool as set forth in claim 1 in which, said punch shank portion cylindrical portion includes an end portion extending to a position adjacent said punch holder bore closed end,   said punch shank portion externally threaded portion being centered on said punch shank portion cylindrical portion,   said punch shank portion externally threaded portion having opposite end portions, and   said punch shank portion cylindrical portion having a pair of reduced diameter portions connected to said opposite end portions of said punch shank portion externally threaded portion.   
     
     
       8. A punching tool as set forth in claim 1 in which, said punch shank portion externally threaded portion is formed by a screw thread insert threaded in a fixed axial position on said punch shank portion, and   said screw thread insert having one end portion secured to said punch shank portion and an opposite end portion extending the length of said punch shank portion in threaded engagement with said punch holder bore to a position adjacent said bore closed end.   
     
     
       9. A punching tool as set forth in claim 1 in which, said punch shank portion externally threaded portion is formed by a screw thread insert threaded in a fixed axial position on said punch shank portion,   said punch end portion torque receiving portion including an enlarged shoulder forming a stop for receiving one end of said screw thread insert on said punch shank portion, and   said screw thread insert extending from said enlarged shoulder the length of said punch shank portion in threaded engagement with said punch holder bore to a position adjacent said bore closed end.   
     
     
       10. A punching tool as set forth in claim 9 in which, said punch shank portion is threadedly advanced into said punch holder bore until said enlarged shoulder abuts said punch holder one end portion preventing further advancement of said punch shank portion into said holder bore.   
     
     
       11. A punch for removable insertion in a holder comprising, an elongated body of a preselected length including a shank portion and a punching end portion extending outwardly from said shank portion for delivering an impact force,   said shank portion having an externally threaded portion and a cylindrical portion,   said shank portion cylindrical portion being positioned between said threaded portion and said punching end portion and extending a preselected length therebetween to stabilize said shank portion for precise location of said punching end portion relative to a holder,   said punching end portion including a torque receiving portion adjacent said cylindrical portion for imparting a rotational force to said shank portion, and   said shank portion threaded portion having an enlarged thread configuration for permitting rapid engagement and disengagement of said shank portion threaded portion in a holder.   
     
     
       12. A punching tool as set forth in claim 11 in which, said shank portion cylindrical portion includes a reduced diameter portion, and   said externally threaded portion extending from said reduced diameter portion so that said shank portion cylindrical portion is separated from said threaded portion by said reduced diameter portion.   
     
     
       13. A punching tool as set forth in claim 11 in which, said torque receiving portion is positioned between said shank portion and said punching end portion, and   said torque receiving portion being formed by a plurality of planar surfaces for receiving a rotational force for advancing and retracting said punch shank externally threaded portion into and out of a holder.   
     
     
       14. A punching tool as set forth in claim 11 in which, said shank portion cylindrical portion includes an end portion,   said shank portion threaded portion being centered on said shank portion cylindrical portion,   said shank portion threaded portion having opposite end portions, and   said shank portion cylindrical portion having a pair of reduced diameter portions connected to said opposite end portions of said shank portion threaded portion.   
     
     
       15. A punching tool as set forth in claim 11 in which, said shank portion externally threaded portion is formed by a screw thread insert threaded in a fixed axial position on said shank portion, and   said screw thread insert having one end portion secured to said shank portion and an opposite end portion extending the length of said shank portion.   
     
     
       16. A punching tool as set forth in claim 11 in which, said shank portion externally threaded portion is formed by a screw thread insert threaded in a fixed axial position on said shank portion,   said torque receiving portion including an enlarged shoulder forming a stop for receiving one end of said screw thread insert on said shank portion, and   said screw thread insert extending from said enlarged shoulder the length of said shank portion.